Disc brake

ABSTRACT

The present invention relates to a disc brake with hydraulically operable brake pads and a mechanical actuating which includes an actuating shaft that is rotatably and sealedly mounted in a bore of a brake housing and acts upon at least one of the brake pads. The present invention focuses on that at least in the area of a shaft duct, a sealing element is provided which is fixed to the actuating shaft so as to rotate along with it and cooperates with at least one associated sealing element and/or mating sealing surfaces in a radial direction. The sealing element bridges a portion of the actuating shaft which is different from the shape of a circle.

TECHNICAL FIELD

The present invention relates to brake systems and more particularlyrelates to disk brake systems having integrated, mechanical actuatingmechanisms.

BACKGROUND OF THE INVENTION

German patent application No. 34 38 209 discloses a disc brake of thistype. The actuating shaft is cylindrically and rotatably mounted in aslide bearing, and a shaft sealing ring is placed in the area of a shaftduct which has a sealing lip that abuts on the periphery of theactuating shaft.

The manufacture of disc brakes of this type necessitates great effortand structure because the actuating shaft necessitates the provision ofa cylindrical abutment surface in the area of the shaft sealing ring, onthe one hand. On the other hand, a recess must be provided in the areaof a pressure member, which is principally carried out by metal-cuttingprocesses. In general, profile bars are meanwhile employed as actuatingshafts having a recess which extends over the total overall length ofthe actuating shaft. This eliminates at least the need to manufacturethe recess. However, no satisfactory solution has been found until nowfor sealing the mounting support of such actuating shafts against theingress of dirt and moisture from outside. This frequently results inactuating shafts stuck with corrosion and, hence, defective disc brakes.

Therefore, an object of the present invention is to provide a reliableand also inexpensive sealing of the mounting support of profiledactuating shafts which permits reliable functioning over the totaluseful life of the disc brakes and, in addition, and minimizes lossesdue to friction.

This object is achieved by the brake system of the present inventionwherein, in the area of a shaft duct, a sealing element is providedwhich is fixed to the actuating shaft so as to rotate along with it andcooperates with associated sealing elements and/or sealing surfaces in aradial direction. Another advantage is achieved because the sealingelement that is movable along with the actuating shaft cooperates withan associated supplementary sealing element and/or an associated sealingsurface also in an axial direction.

The present invention contemplates the combination of profiled actuatingshafts with conventional and customary sealing elements or,respectively, with easy-to-make sealing surfaces. This minimizes thenecessary costs.

Costs may be reduced even further by configuring the sealing element asa bushing, which can be manufactured of sheet metal or plastics materialby way of deepdrawing processes, for example. A bushing provided as asnap-in element can be fitted to the actuating shaft easily and at lowcost.

A functional advantage related to sealings can be achieved by forming acollar to the bushing on the side of the shaft end. Additionally, thecollar includes a sealing surface for the axial abutment of a sealingelement.

The sealing element has a disc-shaped configuration and includesradially outside and axial sealing lips which serve to abut on matingsealing surfaces. This produces together with axial sealing lips aprechamber in front of the radial seal which additionally improves thesealing effect of the sealing element.

In a preferred aspect of the present invention, the sealing elementincludes at least one recess into which a carrier element of theactuating lever is engaged. This achieves an improved connection of thesealing element to the shaft for rotation therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a mechanical actuating mechanism ofa disc brake according to the state of the art.

FIG. 2 is a cross-sectional view of a sealing arrangement of amechanical actuating mechanism according to the present invention in aview like in FIG. 1.

FIG. 3 is a cross-sectional view of a further development of a sealingarrangement of the mechanical actuating mechanism.

FIG. 4 is a cross-sectional view of another variation of the sealingarrangement.

FIG. 5 shows details of a modified embodiment in a view like in FIG. 2.

FIG. 6 is still another modified embodiment of the present invention.

FIG. 7 is a view of a disc-shaped sealing element.

FIG. 8 is a cross-section through a disc-shaped sealing element takenalong the line VI—VI in FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a partial cross-sectional view of a disc brake 1 with amechanical actuating mechanism 2 for hydraulically operable brake pads(not shown). The mechanical actuating mechanism 2 includes an actuatinglever 3 and an actuating shaft 4 which is unrotatably connected to lever3 and is in operative connection to a non-illustrated pressure member.The actuating shaft 4 is rotatably mounted in a bore 5 of the brakehousing 6 within a slide bearing 7 and has, at least in part, across-section different from the shape of a circle. Provided at end 8 ofthe actuating shaft 4 is a collar 9 which serves to abut on anintermediate wall 10 and secures the actuating shaft 4 in position inthe brake housing 6 in an axial direction 11. The other end 12 of theactuating shaft 4 extends out of the brake housing 6 in the area of ashaft duct 13. In a radial direction 14 with respect to the actuatingshaft 4, a shaft sealing ring 15 is installed which protects the slidebearing 7 against the ingress of dirt and moisture from the outside. Asealing lip 16 of the shaft sealing ring 15 which is unrotatably mountedin the brake housing 6 bears against the circumference 17 of theactuating shaft 4. Assisted by a spring 18, the actuating lever 3 withthe shaft 4 is constantly urged into an end position where the actuatinglever 3 with an arm 19 moves to abut a pin 20.

According to the present invention, as is shown in FIG. 2, a sealingelement 21 in the form of a bushing is associated with the actuatingshaft 4 and adapted to rotate with it. Element 21 extends over a recess22 of the actuating shaft 4 at least in part. Thus, the bushing ensuresa circular circumference 17 in the area of the shaft duct 13 whichcooperates in a radial direction 14 with an associated sealing element23 in the form of a sealing ring. On the end close to the lever, thebushing includes a collar 24 which bears against a mating sealingsurface 26 of the actuating lever 3, and a packing washer 25 isinterposed there between. It should be noted that collar 24 and packingwasher 25 are not absolutely necessary when the sealing element 21 isattached to the mating sealing surface 26 in a directly sealing fashion.On its other end, the bushing is positively engaged into a groove 27which is arranged on the circumference of the actuating shaft 4. To thisend, at least one projection 28 is provided on the bushing which extendsradially inwardly and ensures an attachment of the bushing to theactuating shaft 4 for rotation therewith. In addition, each projection28 ensures that the bushing is axially secured in position with respectto the actuating shaft 4. Of course, other types of attachment of thebushing to the actuating shaft 4 may also be provided. The type ofattachment depends especially on which material is chosen for thebushing. For example, bushings made of sheet metal can be caulked,cemented or soldered to the actuating shaft 4. It is also possible tosolder or cement the bushing directly to the mating sealing surface 26of the actuating lever 3 so that the groove 27 becomes unnecessary. Sucha solution is shown in FIG. 6. Further, combinations of theabove-mentioned possibilities are appropriate which ensure an increasedreliability in operation due to improved sealing or fasteningarrangements.

Besides, the embodiment of FIG. 2 shows that the sealing element 23 isarranged in a bore 29 of the brake housing 6 formed fast with thehousing. The sealing element 23 has a first sealing lip 30 whichelastically abuts on the circumference 17 of the sealing element 21 in aradial direction 14, and a second sealing lip 31 which elastically abutson the mating sealing surface 26 of the actuating lever 3 in an axialdirection 11. This produces a chamber 32 between the first and secondsealing lips 30, 31 which isolates the inside space 33 from grosscontaminants. Especially the second sealing lip 31 protects the rollerbearings 34, 35 against small-size contaminants and moisture. Theadvantage of the roller bearings 34, 35 is that they involve low lossesdue to friction, on the one hand, and that they are insensitive tocorrosion, on the other hand. Principally, however, slide bearings mayalso be used without departing from the basic idea of the presentinvention. Moreover, it is self-explanatory that the sealing element 23according to the present invention may have any desired configuration,for example, with a reinforcing ring 36 shaped in it.

The embodiments of FIGS. 3 and 4 are improvements of the sealingarrangement for a mechanical actuating mechanism corresponding to FIG.2. Especially the sealing element 21 configured as a bushing has adesign different from the one in FIG. 2. Exactly as in the variationdescribed hereinabove, the bushing 21 at one end is positively engagedin a groove 27 of the actuating shaft 4 and is thereby reliably retainedthereon. To improve the sealing effect, the bushing 21 has a deflectedcollar 24 at its end close to the shaft end. Advantageously, collar 24has such a radial extension that it provides a sealing surface 60. Asealing lip 31 of the sealing element 23 bears axially against thesealing surface 60. It is preferred that the bushing 21 is made ofstainless steel, and the collar 24 is produced by sheet-metal shaping,for example, in a punching operation. Similarly, the bushing may ofcourse also be made of any other suitable material, such as plastics.Due to the appropriate material selection for the bushing, especiallywhen it is made of stainless steel, the desired surface quality of thesealing surface 60 is achieved. The result is a particularly effectivesealing joint between the bushing 21 and the sealing lip 31. To ensure asealing between the bushing and the actuating lever 3, an additionalpacking washer 25 is enclosed between the collar 24 and the actuatinglever. This additional provision prevents the ingress of dirt betweenthe bushing and the actuating lever 3. According to FIG. 3, the annularpacking washer 25 can be safely positioned by a step 61 in the bushingand pressed against the actuating lever with the pressure needed.

In the sealing arrangement according to FIG. 4, the packing washer 25has a larger extension in a radial direction and is interposed axiallyunder preload between the bushing 21 and the actuating lever 3. Thiseliminates the need for the step 61 on the bushing shown in FIG. 3, andthe result is a simplified bushing design. Similarly to the arrangementsdescribed hereinabove, the collar 24 of the bushing is extended in aradial direction so far that it provides a sealing surface 60 for theaxial abutment of the associated sealing lip 31.

FIG. 5 shows a design wherein the sealing element 21 has the shape of abushing and engages into groove 27 with fingers 38 arranged on the endof resilient arms 37. On the end close to the lever 3, an O-ring 39 isinterposed between the sealing element 21 and the mating sealing surface26. Its purpose is to seal a gap 40 between the actuating shaft 4 andthe sealing element 21. The sealing element 21 is squeezed virtuallyelastically between the mating sealing surface 26 and the groove 27 byway of the elastic O-ring 39. The sealing element 21 may thus beprovided as a plastics component and, with locking engagement in groove27, slipped onto the actuating shaft 4. This arrangement achievesadvantages in terms of assembly.

According to FIG. 6, the bushing-shaped sealing element 21 is solderedor cemented to the mating sealing surface 26 of the actuating lever andfurther has a step 41 used to press an O-ring 42 against a rollerbearing 34, with a spacer ring 43 interposed. A sealing element 23having a V-shaped cross-section bears against the circumference 17 ofthe sealing element 21 in a radial direction 14. Sealing lips areprovided on each leg of the sealing element 23 and bear against themating sealing surface 26 respectively against the brake housing 6. Thesealing element 23 is generally used as a primary seal, while the O-ring42 has the purpose of a main seal. It is principally possible to designthe primary seal and the main seal integrally by shaping the O-ring 42acting as a main seal directly to the primary seal.

The embodiment of FIG. 7 depicts a disc-shaped sealing element 21 whichis slipped on a profiled actuating shaft 4. The sealing element 21 isarranged on the actuating shaft 4 in positive engagement therewithbecause the projection 56 is engaged in the recess 44. Recess 44cooperates with a pressure member (not shown). The embodiment of FIG. 8shows in a cross-sectional view a sealing element 21 arranged in a brakehousing 6 and attached to an actuating shaft 4. The sealing element 21includes two radially external sealing lips 45, 46 and two axial sealinglips 47, 48. The sealing lips 45, 46, 47, 48 are adapted for abutment onassociated mating sealing surfaces 49, 50, 51 which are arranged on theactuating lever 3 or the brake housing 6. Thus, the sealing element 21provides a sealing both in an axial direction 11 and a radial direction14. Recesses 53, 54 for engagement by cam-shaped carrier elements 55 ofthe actuating lever 3 are provided on each end surface 52. This achievesan unrotatable connection of the sealing element 21 and the actuatingshaft 4, and prevents the sealing element 21, which is preferably madeof an elastic material such as EPDM, for example, from being deformed inthe area of the recess 44 to an unacceptable degree.

It should be noted that many variations of the sealing element 21 arepossible without departing from the basic idea of the present invention.

What is claimed is:
 1. Disc brake with hydraulically operable brakepads, comprising: a brake housing, a mechanical actuating mechanismincluding an actuating shaft that is rotatably and sealedly mounted in abore of the brake housing and acts upon at least one of the brake pads,a sealing element which is fixed to the actuating shaft such that saidsealing element rotates with said shaft, whereby said sealing elementcooperates with associated sealing elements or sealing surfaces in aradial direction, wherein the actuating shaft has a cross-section whichdiffers at least in part from the shape of a circle radially inward ofsaid sealing element.
 2. Disc brake as claimed in claim 1, wherein thesealing element which is fixed to the actuating shaft so as to rotatealong with it, cooperates with associated sealing elements or sealingsurfaces in an axial direction.
 3. Disc brake as claimed in claim 1,wherein the sealing element extends at least in part over a recess inthe actuating shaft.
 4. Disc brake as claimed in claim 1, wherein thesealing element bears against a mating sealing surface in an axialdirection close to the shaft end.
 5. Disc brake as claimed in claim 1,wherein the sealing element bears against an actuating lever close tothe shaft end.
 6. Disc brake as claimed in claim 1, wherein the sealingelement is configured as a bushing.
 7. Disc brake as claimed in claim 1,further including an additional sealing element disposed between amating sealing surface and the sealing element.
 8. Disc brake as claimedin claim 1, wherein a bushing includes a collar close to the shaft end.9. Disc brake as claimed in claim 8, wherein the sealing elementcooperates with the collar close to the shaft end in an axial direction.10. Disc brake as claimed in claim 1, wherein the actuating shaftincludes a groove on the circumference into which the sealing element ispositively engaged.
 11. Disc brake as claimed in claim 1, wherein thesealing element includes resilient arms and fingers which engage into agroove.
 12. Disc brake as claimed in claim 1, wherein the sealingelement has a disc-shaped configuration and includes radially outsidesealing lips for abutment on a mating sealing surface.
 13. Disc brake asclaimed in claim 1, wherein the sealing element includes axial sealinglips for abutment on mating sealing surfaces.
 14. Disc brake as claimedin claim 1, wherein the sealing element with a projection is positivelyengaged in a recess of the actuating shaft.
 15. Disc brake as claimed inclaim 1, wherein the sealing element includes at least one recess intowhich a carrier element of the actuating lever is engaged.